First generation wireless link systems for portable listening devices, such as hearing aid devices and mobile devices, have typically been based on fixed transmitted power between the devices. The transmitter current is, e.g. in the production phase, (conservatively) aligned to the minimum current with which the system always can achieve internal communication, taking into account component tolerances, different operational distances between devices because of variation in head sizes placement of the mobile device relative to a hearing aid device, etc. The overhead in current in a particular setup represents a waste of power for those devices.
EP2211579 B1 describes a communication system comprising a first and a second portable communication device, each comprising transmit and receive units for establishing a wireless link between the devices, wherein at least the first communication device is a portable listening device and comprises a control unit for dynamically adjusting the transmit power of its transmit unit (TX) based on a measure (LQ) of the quality of the link provided by a link quality evaluation unit. The link quality evaluation unit of the receiving device is adapted to combine one or more link quality measures for determining an appropriate transmit power level for the transmitting device.
For example, the AGC settings are combined with a CRC-check, e.g. in such a way that only AGC settings for error-free frames are stored and used for the estimate of link quality, or the AGC settings are combined with a BER measure.